Variable transconductance electron tube



Aug. 14, 1962 E. F. BRANAGAN 3,049,671

VARIABLE TRANSCONDUCTANCE ELECTRON TUBE Filed March 31, 1959 M P g R 5 n f l3 6 '4 a f |7 0 o I ii b A U=EJ-'EJ=D c w F IG.3. f

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EDWARD F. BRANAGAN United States Patent Ofilice 3,049,671 Patented Aug. 14, 1962 3,049,671 VARIABLE TRANSCOlfjDgCTAN CE ELECTRON T B Edward F. Branagan, Rockville, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed Mar. 31, 1959, Ser. No. 803,334 6 Claims. (Cl. 328-158) (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to an electron tube structural arrangement and more particularly to such an arrangement for obtaining a variable transconductance characteristic correlative to the input intelligence signal.

In accordance with the instance invention, variation in the transconductance of a diode, triode or other multielement tube is accomplished by means of a special anode. Such a tube includes a plate electrode of particular composition or geometrical configuration, conventional filaments, cathode, and two pairs of deflection electrodes within an evacuated envelope. By the use of a particular plate electrode composition and/ or configuration, diverse transconductance characteristics, i.e., linear logarithmic, step function, etc., can be obtained correlative to predetermined input signals on the deflection electrodes which direct the cathode emitted electron beam to particular portions of the plate electrode. The deflection of the cathode stream and focusing of the electron beam are accomplished as in conventional cathode ray tubes. Furthermore, the electron stream from the cathode may or may not, as the case may be, be accelerated by conventional accelerating electrodes as in standard cathode ray tubes.

The purpose in changing the transconductance is to obtain an output signal similar to the input signal or one that is a mathematical function or a complex function of the input signal.

Prior to the invention disclosed herein such complex outputs as a function of input signal have been achieved by using resistor, capacitor, and/or inductance networks with conventional tubes such as diodes, triodes, pentodes, etc. The prior methods have therefore required considerably more complex circuitry and space. The wide variations of output signal vs. input signal achieved herein cannot be accomplished in many engineering applications with the older methods.

The older methods obtained amplification by varying an electrode or grid potential placed between the anode and cathode. This grid potential is varied with respect to the cathode as a function of the input signal. The best tubes available at present have relatively low input impedances for circuit applications requiring very high input signal impedance.

It is therefore an object of this invention to provide a new and improved electron tube structural arrangement.

It is another purpose of this invention to provide an electron tube structural arrangement for obtaining a variable transconductance characteristic correlative to the input signal.

It is a further object of this invention to provide an electron tube of the aforementioned character providing direct conversion of any type signal source to a particular output function of the same or greatly amplified magnitude.

It is a still further object of this invention to provide an electron tube characterized by a high input impedance and a small power requirement.

Another object of this invention is to provide an electron tube capable of converting an input signal into a desired complex output signal without the use of elaborate circuitry.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

FIG. 1 is a circuit diagram employing the new electron tube which serves to illustrate the input and output connections thereof, and the structure within the tube.

FIGS. 2a through 2 inclusive, illustrate preferred resistive anode configurations; and

FIGS. 3a through 3h, inclusive, illustrate various anode geometries suitable for use in the new tube structure.

Referring now to FIG. 1 there is shown at 1 the electron tube of the instant invention. Within the envelope of tube 1 is an anode 2, cathode 3, horizontal and vertical deflection plates 4, 5, 6 and 7, and an accelerating electrode 8 for the cathode electrons. Each of the deflection plates, 4, 5, 6 and 7 is connected to input terminals 11, 12, 13 and 14, respectively. Accelerating electrode 8 is connected to terminal 15. The anode 2 is series connected through a load resistance 16 and battery 17 to the cathode 3.

The resistive anode 2 may be made of numerous resistive materials such as carbon, conductive ceramic, resistive glass, metal or, a semiconducting material. The resistive anode may be nonlinear over its surface or linear, as desired. It may be made to give nonlinear characteritsics such as logarithmic, semi-log, a special mathematical function or an empherical function. This resistive anode may be molded, printed, sprayed, etched, photoprinted, or fabricated, etc., to achieve the particular resistive characteristic or complex function desired.

In FIGS. 2a through 2 there are illustrated a number of configurations for the aforesaid anode. These are included by way of example only and obviously other configurations will suggest themselves to those skilled in the art. FIG. 2a illustrates a configuration suitable for achieving a cosine, tangent, sin 0+cos 0, or (tan 0) etc., output. FIG. 2b is illustrative of a configuration for achieving a step function output. The configuration shown in FIG. 20 will provide a linear output while that output while that of FIG. 2 provides an empirical output. It should be noted that such a spiral configuration may be made to vary as to width, rate of change of width, thickness, composition, etc. The particular configurations of FIG. 2 show variations of the anodes in planes perpendicular to the stream of electrons as they leave the cathode 3. Thus, if the stream of electrons produced by the cathode is directed in a horizontal plane, the illustrated anode configurations will be in the vertical plane.

In carrying out the instant invention, the resistive anode may be bent, molded or fabricated in any manner to give various three-dimensional configurations such as shown in FIG. 3. FIGS. 3a through 3h inclusive are included by way of example only to illustrate various geometrical configuration to achieve a particular output. In addition to using a particular configuration as shown in FIG. 3, the resistive composition may be as described above.

In FIGS. 2 and 3 the arrow in each represents the anode connection. This has been illustrated in the center of each anode configuration, however, it is to be understood that this connection could be placed at any point on the anode as desired, including the end termination.

As should now be apparent, the electron beam, accelerated by electrode 8, is deflected by one of the horizontal or vertical deflection plates and strikes the anode at a particular location thereon depending upon the input signal applied to one or more of the plates. Although an electrostatic deflection system has been illustrated, it is to be understood that magnetic deflection coils could be employed. The incoming signal or signals may be placed on one or more of the plates. The deflection plates employed give a very high input impedance. The acceleration potential applied to the electrode 8 may be high, medium or low as desired.

For a better understanding of the operation of the new and unique tube structure herein disclosed, assume a signal of sine wave input into the deflection plates and 7; a load resistance 16 of 500,000 ohms; a battery 17 voltage of 100 volts; and a linear resistive characteristic on either side of the anode terminal P of 500,000 ohms i.e., PM =PR=500,000 ohms. With no input signal applied to deflection plates 4 and 6, assume a ten volt input signal applied to plates 5 and 7 will deflect the electron beam by a magnitude of 10% of the distance PM or PR. With a Zero input signal applied to the terminals 11 and 13 the current across the load resistor 16 will be equal to where L is the resistance from point P to the point on the anode where the deflected electron beam strikes (example, with maximum deflection L=PM or PR). With a zero input signal applied to terminals 12 and 14 the electron beam will be centered at P. Hence, L in the above equation is equal to zero and i =20 10- When the input signal is a maximum, i.e. 10 volts, the electron beam is deflected 10% to the right or left of P on the anode of FIG. 1. This introduces a series resistance into the circuit of 50,000 ohms (10% of PM or .10 500,000=50,000). From the above equation for i it can now be seen that It should now be evident that the current across the load 16 has changed by 1.9 10 amps.

Such a current change through the load may be much greater or less depending upon the desired application of the tube. Furthermore, the tube may be designed so that at zero signal input current through the tube is not a maximum, as above, but may be made to be any desired value by suitable choice of anode connection, composition or geometry.

From the foregoing it should be apparent that an 4 entirely new and unique tube structure has been disclosed for providing any simple or complex output therefrom The output amplitude and/or wave form may be ditferent from the input signal simply by the choice of a particular anode as herein described.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An electron tube having a non-linear input versus output characteristic comprising a cathode for emitting an electron beam, an anode of resistive material for receiving said electron beam and having a geometrical configura tion that provides a non-linear resistance characteristic in three dimensions, a single electrical connection to said anode for applying a potential thereto and receiving the output therefrom, and an accelerating electrode located between said cathode and said anode and adjacent to said cathode, four orthogonally arranged electrostatic deflecting plates located between said accelerating electrode and said anode, the oppositely located plates being arranged in pairs whereby deflection of the electron beams causes said tube to have a non-linear output commensurate with the geometrical configuration of said anode.

2. The apparatus of claim 1 wherein said tube is connected in a circuit, said circuit comprising a load resistor having one end connected to said anode, a source of potential connected between the other end of said resistor and said cathode, means for connecting a first electrical input signal across one pair of said deflecting plates, means for connecting a second electrical input signal across the other pair of said deflecting plates whereby an output signal is developed across said load resistor indicative of said first and second input signals and the geometrical configuration of said anode.

3. An electron tube as in claim 1 wherein said resistive material is carbon.

4. An electron tube as in claim 1 wherein said resistive material is conductive ceramic.

5. An electron tube as in claim 1 wherein said material is resistive glass.

6. An electron tube as in claim 1 wherein said anode is comprised of semi-conducting material.

References Cited in the file of this patent UNITED STATES PATENTS 2,071,382 Balsley Feb. 23, 1937 2,237,671 Kallmann Apr. 8, 1941 2,474,960 Skellett July 5, 1949 2,884,561 Beste Apr. 28, 1959 

